Simple amine compounds are known to provide neutralizing, dispersant and hardening properties when added to coatings, mineral slurries and epoxy formulations. Methods for simple amine compound manufacture are well-documented and known in the art, and when the goal is to prepare primary amines, the preferred routes often involve intermediate nitro alcohol compounds. For various reasons, it would be advantageous to have compounds with more than one amino group and low volatile organic compound (“VOC”) content.
Volatile organic compounds are organic chemical compounds that have high enough vapor pressures under normal conditions (i.e., 1 atmosphere and 25° C.) to significantly vaporize and enter the atmosphere. They include a variety of chemicals, many of which have adverse health effects, and are emitted by a wide variety of products including but not limited to: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions. Minimization of VOC content has become the focus of public attention as well as government regulation.
Processes for the manufacture of the intermediate nitro alcohol compounds, are known and typically involve nitro aldol reaction (Henry Reaction) between nitroalkanes and aldehydes. There has been occasional reference to the preparation of dinitro alcohols involving a tandem Michael addition and Henry reaction of a nitroalkane with an α,β-unsaturated aldehyde. For example, see “Secondary dinitro alcohols,” Smith, Curtis W. (Shell Development Co.) 1949, and U.S. Pat. No. 2,475,996, which describe the manufacture of the nitro alcohol 2,5,6-trimethyl-2,6-dinitro-3-heptanol. This nitro alcohol is also prepared as an intermediate to making a vasopeptidase inhibitor, as discussed in Efficient Asymmetric Synthesis of the Vasopeptidase Inhibitor BMS-189921 by Janak Singh et al., Org. Lett. (2003), 5, 17, 3155-3158. In addition, manufacture of the nitro alcohol compound 2,6-dinitro-5-phenyl-heptan-3-ol has been described in David St. Clair Black et. al. Australian Journal of Chemistry, 1976, 29(11), 2511. As is also well-established, nitro alcohol compounds may be readily converted to the aminoalcohol compounds by hydrogenation with hydrogen over a suitable catalyst, for example Raney nickel or a platinum- or palladium-based catalyst (Pt or Pd in elemental form or as oxides, with or without supports, e.g., carbon). Those skilled in the art are also aware that other reducing agents which will reduce nitroalkanes to primary amines include metal/acid combinations, e.g., iron/acetic acid; and aluminum hydrides. The preferred reducing agents include hydrogen gas in combination with any of the following catalysts: Raney nickel, platinum or palladium.
Diamino alcohol compounds and their uses, on the other hand, are not currently represented in the prior art.
The diamino alcohol compounds described herein will perform excellently as dispersants in mineral slurry systems, particularly in aqueous kaolin clay slurries having high solids content (i.e., greater than 50 weight % solids) while maintaining fluidity necessary for handling. Calcined kaolin is an anhydrous aluminium silicate produced by calcining (heating) ultrafine natural kaolin material to high temperatures (700° C.-1000° C.) in a kiln. The calcination process increases whiteness and hardness, improves electrical properties, and alters the size and shape of the kaolin particles. Calcined kaolin is useful for improving the thermal properties of agricultural films, improving the electrical performance of poly(vinyl)chloride cable, providing a functional filler in thermoplastic materials, and as an additive to impart opacity to paints.
To date, polyacrylate salts have been employed as dispersing agents in mineral slurries, such as kaolin clays, to impart fluidity since the system will not flow in the absence of a dispersing agent. Polyacrylate salts have good handling and safety characteristics, but only allow for limited dispersive capabilities as the content of solids in the system is increased. Simple diamines such as ethylenediamine have rheological limitations when higher solids loadings are encountered, while longer-chain diamines become highly colored and have a very offensive odor. Simple amino alcohols, such as 2-amino-2-methyl-1-propanol (AMP), do not have a high degree of adsorption to the surface of calcined clay, and have low efficiency as surface treatments or sole dispersants. There is a need for new dispersing agents that can provide aqueous kaolin clay slurries (preferably calcined kaolin clay slurries) having high solids (>50% solids). It is another object of this invention to provide higher solid aqueous calcined clay slurries that are sufficiently fluid and do not require multiple dispersant technologies that do not achieve the desired level of fluidity at increased solids loading.